1. Field of the Invention
This invention relates generally to optical communication systems. More particularly, the invention pertains to a system for testing optical communication systems, subsystems and components.
2. Description of the Background Art
Opto-electronic components, including fiber optic cables, connectors, transmitters, receivers, switches, routers and all other types of optical components have become the backbone of the modern telecommunication infrastructure. Due to their relatively low error rate and wide bandwidth, optical communication systems have supported an explosion in the growth of data communication systems, such as the Internet. With the Internet in its infancy, it is expected that the reliance on optical components and systems will only increase as the Internet becomes more closely intertwined with mainstream business and consumer applications.
Although the technology associated with optical communication systems and components has greatly advanced over the last decade and the use of such technology has accelerated, the technology associated with testing optical communication systems and components has greatly lagged.
An optical communication system is only as fast and reliable as the worst component within the system. Each component and/or subsystem within the system must be tested to ensure that it meets minimum technical standards that have been set in the industry. In order to ensure that a particular component, subsystem or system meets or exceeds technical standards, that component, subsystem or system must be tested. This involves a tedious and time-consuming process that leads to human error.
A known testing scheme 10 is shown in FIG. 1. The scheme 10 typically includes an optical transmitter 12, an optical attenuator 14, an (optional) optical monitor 16 and a optical receiver 18. A device under test 25 (DUT) is placed between the transmitting side 20, (which comprises the transmitter 12, the attenuator 14 and the optical monitor 16), and the receiving side 22, (which comprises the receiver 18). These components 12, 14, 16, 18 are separately specified, purchased and calibrated. These components are then interconnected with fiber optic cables 24, connectors 26 and splitter 28.
In order to test the bit error rate (BER), or sensitivity, of the DUT 25, a technician energizes the optical transmitter 12 and starts transmitting at a level of optical power which is sufficient for the DUT 25 to process without errors. The optical signal is transmitted from the optical transmitter 12, through the optical attenuator 14, through the DUT 25 and is received by the optical receiver 18. The technician measures at the optical receiver 18 the number of errors received during the transmission between the optical transmitter 12 and the optical receiver 18. During a typical testing regimen, the technician sends the test signal at a certain optical power, measures the number of errors and, using the attenuator 14, subsequently attenuates the test signal to a lower optical power as seen by the DUT 25. The technician then measures the number of errors at this lower optical power. This process is repeated over a range of optical powers that is suitable for the DUT 25.
This testing scheme, which has not fundamentally changed since the origins of the fiber optic communication industry, has disadvantages. First, each of the components must be separately specified and purchased. Each of these components must then be separately tested and calibrated, and then all the components must be assembled and then tested.
The assemblage of multiple optical components also poses a problem due to the number of optical interfaces. Optical interfaces, which are the interfaces between one optical component and another, typically include a piece of optical equipment and a fiber optic cable or connector. It is often tedious to recalibrate the entire optical system in order to account for the losses introduced because of these optical interfaces.
Given such an arrangement of equipment, due to the number of individual pieces of testing equipment, the size of each piece of testing equipment and the delicacy of the entire testing arrangement, this testing scheme is generally used in an optical laboratory environment. As a practical matter, it is almost impossible to test a piece of operating equipment installed in the field with this scheme. If a piece of optical equipment must be tested, the equipment must be physically removed from the field and brought to the laboratory for testing.
An additional drawback with such an arrangement is cost. Each piece of equipment is expensive. What drives this expense is the redundancy in the number of components, i.e., power supplies, display screens, controlling microprocessors and the housing for all of these separate optical components.
Accordingly, typical testing schemes in the optical industry are time consuming, expensive and cumbersome. An inexpensive testing unit which greatly simplifies the testing of optical components is thus needed.